My choice is not medicine, but since my father is a doctor and I know many doctors/medical students/class fellows aiming to be doctors, I can comment on it. I don't know about the whole world
But I'm fairly certain that between the subcontinent and most first world countries (US, UK and Australia to be fair), you have a better choice in the subcontinent. You want to know why? There are quite a few reasons:
1. Cheaper education. Most government-owned universities have nominal fee which can be paid by almost anyone. Even private institutions are quite accessible. When you look at universities abroad, however, the cost hits the roof.
2. Some of the excellent doctors around are available. I know you would disagree, since obviously the general quality of education abroad is better, but when it comes to medicine subcontinent is definitely in the league. There's a simple equation: Indian/Pakistan doctors see almost ten-fold more patients than a first world any day. He experiences diagnosing and dealing with a huge variety of illnesses, from cholera to AIDS, while abroad there are much scarcer cases of these illnesses because of better health facilities and a smaller population. You are hence, interacting with people who have greater experience with patients than a doctor abroad.
3. For the same reason, you are able to interact better with your patients throughout your MBBS program and house job. You learn a lot more about the subject.
4. Although you haven't asked about jobs, but there are more job opportunities in the subcontinent and you have greater job security. Most of the laws abroad are rather stringent and a slightest error in treatment can have your medical license revoked. No kidding; I'm not saying there's no security there but it's not as strict in the subcontinental area. This may sound wrong of me, but coming from a rather reckless person who can panic easily, I would prefer working in an environment where there isn't a lawyer and a policeman around me all the time.
If you want to study in the first world countries, I would suggest you specialize after your MBBS degree. Give an USMLE exam and continue your residency and specialization abroad if you like. But for MBBS, I recommend the subcontinent. I can't comment on African/East American/East Asian countries, though.